Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 70 for “"amorphous silica"”.
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Biologically Controlled Mineralization and Demineralization of Amorphous Silica
… awaiting development upon a barren landscape. Silica biomineralization is one of these emerging frontiers. As new information about the chemical and structural nature of the macromolecules involved in biosilicification is revealed, the means these species employ to control the temporal and …
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The dissolution rates of amorphous silica and opal-CT
Dissolution rates of two different glasses (soda-lime glass and fused quartz) and a natural opal (opal-CT) in distilled and deionized water and two concentrations of NaCI solution from 25°C to 75°C were measured by molybdate blue method and determined by initial rate method. The specific surface …
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The Safety and Immunostimulatory Properties of Amorphous Silica Nanoparticles <10 nm in Diameter
Humans are exposed to high levels of amorphous silica on a daily basis, via the diet and the use of cosmetic and pharmaceutical products. Amorphous silica particles (10-200 nm) have also been developed for use in biomedical applications, including as binding agents in tissue repair, drug and gene …
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Novel amorphous silica and silica xerogels for the adsorption of organic pollutants from water
… hydrophilic and hydrophobic samples of the novel amorphous silica Quartzene and on silica xerogels, synthesised by a low cost and environmentally friendly synthesis, inspired from the work of Bangi, Rao A.P., Hirashima and Rao A.V. [1]. All adsorbents used in this study were also characterised by …
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Effects of water on chemomechanical instabilities in amorphous silica : nanoscale experiments and molecular simulation
We elucidate the tensile failure mechanism of amorphous silica and the effects of water on the process, combining: (a) atomic force microscope (AFM) bending tests, (b) molecular dynamics (MD) simulation and (c) molecular orbital (MO) simulation. Bending tests of silica nanowires provide validation …
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Characterization of amorphous silica and crystalline silica from rice husk ash on water filtration application
… at low-cost production and using an effectively silica from natural waste rice husk was evaluated. Rice husk was fired at 700ºC and 1000ºC respectively and produced rice husk ash which mutated to amorphous and crystalline silica. Five samples were fabricated after been mixed with the compositions …
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Amorphous silica-based carbon nanotube and silver nanoprism coatings: synthesis and investigation of their optical properties /
In this thesis two type silica composite coatings were investigated which includes (i) silica-single-walled carbon nanotube (SWCNT) and (ii) silica-silver nanoprism (AgNPR) coatings. Research results showed, that the highest colloidal stability of SWCNTs in ethanol is obtained with surfactant P4VP. …
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Application of Fourier-transformed-infrared spectroscopy to quantitate amorphous silica in personal air samples in sugarcane cutters
… containing various contaminants, including amorphous silica. In sugarcane, the leaves and other excess plant material contain amorphous silica that can be released into the worker's environment during harvest. Quantitating this amorphous silica and determining if it can play a deleterious …
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Ultrahigh Vacuum Studies of the Fundamental Interactions of Chemical Warfare Agents and Their Simulants with Amorphous Silica
… of the agent without the toxic effects, with amorphous silica were conducted to investigate how small changes in chemical structure affect the overall chemistry. Experiments investigating the surface chemistry of two classes of CWAs, nerve and blister agents, were performed in ultrahigh vacuum …
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Dimerization of naphtha-range Fischer-Tropsch olefins into diesel-range products over zeolite H-ZSM-5 and amorphous silica-alumina
… in the liquid phase, over zeolite H-ZSM-5 and an amorphous silica-alumina (ASA) catalyst. Both catalysts were in the form of extrudates.
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Reaction of meta-diisopropylbenzene on acid molecular sieves and synthesis of zeolites by a vapor phase transport method
… faujasite (hex and FAU), L, SAPO-37, and an amorphous silica-alumina at temperatures around 463 K in a flow-type fixed-bed reactor. A small amount of cracking is observed. The main reactions of meta-diisopropylbenzene are isomerization and alkylation. This alkylation is proposed as a new test …
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Probing the Hydrogen Bonding Interaction at the Gas-Surface Interface using Dispersion Corrected Density Functional Theory
… the chemical warfare agent sulfur mustard with amorphous silica were investigated using electronic structure calculations. In this thesis, the binding energies of sulfur mustard and mimic species used in the laboratory were calculated using density functional theory and fully ab initio …
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Silica dissolution at low pH in the presence and absence of fluoride
… Of particular importance are the interactions of silica with aqueous fluids because these fluids are present in nearly every natural setting. The dissolution of silica and glass by HF plays a very important role in technology and is widely used for the etching of silica and silicate glasses in the …
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Production of mid-chain branched detergent-range olefins over shape-selective acid catalysts
… a range of acid catalysts (MFI, BEA, TON and amorphous silica-alumina) were screened for the dimerization of 1-hexene, under generally mild conditions, viz. 150 - 170°C, 20 - 40 bar and 1 - 4h-1 WHSV. It was postulated that shape-selective catalysts with defined pore sizes might improve …
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Silica diagenesis and its pore-scale influence on the characteristics of the upper and lower Bakken shales, Williston Basin, North Dakota and Montana
… and contain a significant portion of biogenic silica in the form of radiolaria. Biogenic silica dissolution and reprecipitation is known to contribute to the development and/or preservation of pore space, ultimately affecting source rock quality and reservoir recoverability. In general, silica …
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Novel inorganic membranes for gas separation
… zeolite, carbon, polymeric, mixed matrix, amorphous silica, and supported ionic liquid membranes. Supported ionic liquid CO₂/CH₄ selective membranes were synthesized in our laboratory by applying room temperature ionic liquids (RTILs) to porous inorganic α-alumina supports. The supported …
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Methanol amination over hydrothermally treated zeolites RHO and Modernite
… of methanol or dimethyl ether and ammonia over amorphous silica-alumina. This process involves large separation and recycle units which are both costly and energy intensive as the separation requires azeotropic distillation at 15 bar. Methylamines can be formed over other solid acid catalysts …
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Hydrated silica on Mars: Global comparison and in-depth analysis at Antoniadi Crater
Hydrated silica is found in a variety of Martian deposits within suites of minerals that indicate aqueous alteration, mostly because hydrated silica forms easily in different environments. Because of its relative ubiquity on Mars, it makes a good tracer mineral to compare otherwise dissimilar …
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Characterisation of silica in Equisetum hyemale and its transformation into biomorphous ceramics
… wood during the past time due to its high silica encrustations in the epidermis. Equisetum hyemale (scouring rush) can accumulate silica up to 16% dry weight in its tissue, which makes this plant an interesting candidate as a renewable resource of silica for the synthesis of biomorphous …
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